A file system is a way of organizing data for persistent storage. The file system is broken into user data, the data a user expects to see when requesting a file and metadata, the data that defines the internal hierarchy of the file system.
In file systems errors occur for a number of reasons. Software logic errors, checksum errors or media errors cause inconsistencies within the metadata responsible for describing the internal structure of the file system.
The file system will eventually attempt to process the metadata with inconsistencies or errors that will likely cause the file system to crash. When this occurs, a conventional file system recovery tool is executed to set the metadata objects within the file system to a consistent state. The length of time the conventional file system recovery runs is dependent upon the size of the file system and the number of metadata objects within the file system that must be corrected to set the file system to a consistent state.